U.S. patent application number 16/756402 was filed with the patent office on 2020-10-01 for water-dispersible sheet.
The applicant listed for this patent is Nippon Paper Industries Co., Ltd., NIPPON PAPER PAPYLIA CO., LTD.. Invention is credited to Yoshiaki Ishino, Masaki Kishimoto, Yasuaki Matsumori.
Application Number | 20200308453 16/756402 |
Document ID | / |
Family ID | 1000004917807 |
Filed Date | 2020-10-01 |
United States Patent
Application |
20200308453 |
Kind Code |
A1 |
Kishimoto; Masaki ; et
al. |
October 1, 2020 |
WATER-DISPERSIBLE SHEET
Abstract
A water-dispersible sheet with improved water dispersibility is
provided. Provided is paper-making fibers containing two kinds of
compounds, a specific alkalized fibrous carboxyalkyl cellulose and
a specific carboxyalkyl cellulose salt. That is a water-dispersible
sheet comprising a papermaking fiber and an alkalized fibrous
carboxyalkyl cellulose and further comprising a carboxyalkyl
cellulose salt, wherein the degree of etherification of the fibrous
carboxyalkyl cellulose is 0.2 to 0.6, the degree of etherification
of the carboxyalkyl cellulose salt is 0.5 to 1.6, the viscosity of
1% aqueous solution of the carboxyalkyl cellulose salt measured by
Brookfield viscometer is 2 to 200 mPa-s, and the ratio of the
carboxyalkyl cellulose salt to the sum of the papermaking fibers
and the alkalized fibrous carboxyalkyl cellulose is 0.1 to 10% by
weight.
Inventors: |
Kishimoto; Masaki; (Tokyo,
JP) ; Ishino; Yoshiaki; (Tokyo, JP) ;
Matsumori; Yasuaki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIPPON PAPER PAPYLIA CO., LTD.
Nippon Paper Industries Co., Ltd. |
Shizuoka
Tokyo |
|
JP
JP |
|
|
Family ID: |
1000004917807 |
Appl. No.: |
16/756402 |
Filed: |
November 29, 2018 |
PCT Filed: |
November 29, 2018 |
PCT NO: |
PCT/JP2018/043941 |
371 Date: |
April 15, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J 2301/41 20200801;
B41M 5/41 20130101; C09J 7/29 20180101; D21H 27/00 20130101; C09J
2203/334 20130101; D21H 15/10 20130101; C09J 7/21 20180101; D21H
17/26 20130101; C09J 2400/28 20130101 |
International
Class: |
C09J 7/29 20060101
C09J007/29; D21H 27/00 20060101 D21H027/00; D21H 15/10 20060101
D21H015/10; D21H 17/26 20060101 D21H017/26; C09J 7/21 20060101
C09J007/21; B41M 5/41 20060101 B41M005/41 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2017 |
JP |
2017247603 |
Claims
1. A water-dispersible sheet comprising a papermaking fiber and an
alkalized fibrous carboxyalkyl cellulose and further comprising a
carboxyalkyl cellulose salt, wherein the degree of etherification
of the fibrous carboxyalkyl cellulose is 0.2 to 0.6, the degree of
etherification of the carboxyalkyl cellulose salt is 0.5 to 1.6,
the viscosity of 1% aqueous solution of the carboxyalkyl cellulose
salt measured by Brookfield viscometer is 2 to 200 mPa-s, and the
ratio of the carboxyalkyl cellulose salt to the sum of the
papermaking fibers and the alkalized fibrous carboxyalkyl cellulose
is 0.1 to 10% by weight.
2. The water-dispersible sheet of claim 1, wherein the Canadian
standard freeness of the papermaking fiber is 200 to 750 ml
CSF.
3. The water-dispersible sheet of claim 1, wherein a tacky adhesive
layer is installed on one of the surfaces.
4. The water-dispersible sheet of claim 3, wherein a
thermosensitive recording layer is installed on the surface of the
sheet opposite to the surface on which the tacky adhesive layer is
installed.
5. The water-dispersible sheet of claim 3, wherein an aqueous
coating material is applied on the surface of the sheet opposite to
the surface on which the tacky adhesive layer is installed.
6. A method for preparing the water-dispersible sheet of claim 1,
wherein the method comprises: (1) preparing a sheet with a
papermaking raw material comprising papermaking fibers and fibrous
carboxyalkyl cellulose, and (2) applying an alkalinizing agent on
the papermaking raw material obtained in step (1), and (3) applying
a carboxyalkyl cellulose salt on the papermaking raw material
obtained in step (2) or (2') applying a carboxyalkyl cellulose salt
on the papermaking raw material obtained in step (1); and (3')
applying an alkalinizing agent on the papermaking raw material
obtained in the step (2').
7. The method of claim 6, wherein the steps (2) and (3) are
performed simultaneously, or the steps (2') and (3') are performed
simultaneously.
8. The method of claim 6, further comprising the step of installing
a tacky adhesive layer on one of the surfaces of the
water-dispersible sheet.
9. The method of claim 8, further comprising the step of applying
an aqueous coating material on the surface of the water-dispersible
sheet opposite to the surface on which the tacky adhesive layer is
installed.
10. The method of claim 8, further comprising the step of
installing a thermosensitive recording layer on the surface of the
water-dispersible sheet opposite to the surface on which the tacky
adhesive layer is installed.
11. The water-dispersible sheet of claim 2, wherein a tacky
adhesive layer is installed on one of the surfaces.
12. The water-dispersible sheet of claim 11, wherein a
thermosensitive recording layer is installed on the surface of the
sheet opposite to the surface on which the tacky adhesive layer is
installed.
13. The water-dispersible sheet of claim 11, wherein an aqueous
coating material is applied on the surface of the sheet opposite to
the surface on which the tacky adhesive layer is installed.
14. A method for preparing the water-dispersible sheet of claim 2,
wherein the method comprises: (1) preparing a sheet with a
papermaking raw material comprising papermaking fibers and fibrous
carboxyalkyl cellulose, and (2) applying an alkalinizing agent on
the papermaking raw material obtained in step (1), and (3) applying
a carboxyalkyl cellulose salt on the papermaking raw material
obtained in step (2) or (2') applying a carboxyalkyl cellulose salt
on the papermaking raw material obtained in step (1); and (3')
applying an alkalinizing agent on the papermaking raw material
obtained in the step (2').
15. The method of claim 14, wherein the steps (2) and (3) are
performed simultaneously, or the steps (2') and (3') are performed
simultaneously.
16. The method of claim 15, further comprising the step of
installing a tacky adhesive layer on one of the surfaces of the
water-dispersible sheet.
17. The method of claim 14, further comprising the step of
installing a tacky adhesive layer on one of the surfaces of the
water-dispersible sheet.
18. The method of claim 17, further comprising the step of applying
an aqueous coating material on the surface of the water-dispersible
sheet opposite to the surface on which the tacky adhesive layer is
installed.
19. The method of claim 16, further comprising the step of applying
an aqueous coating material on the surface of the water-dispersible
sheet opposite to the surface on which the tacky adhesive layer is
installed.
20. The method of claim 16, further comprising the step of
installing a thermosensitive recording layer on the surface of the
water-dispersible sheet opposite to the surface on which the tacky
adhesive layer is installed.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a water-dispersible sheet
with an improved water dispersibility, and more particularly to a
water-dispersible sheet comprising a tacky adhesive layer on one of
the surfaces and a coating layer, such as a thermosensitive
recording layer or an inkjet recording layer, on the other
surface.
BACKGROUND OF THE INVENTION
[0002] Water-dispersible paper (also referred to as
water-disintegrable paper or water-soluble paper), which is rapidly
dispersed in water, is widely used for applications such as
filter-wrapping paper of cigarettes, wrapping paper, confidential
document paper, water-dispersible labels (References 1, 2 etc.). As
one of these, a water-dispersible label has a structure in which a
coating layer such as a thermosensitive recording layer or an
ink-jet recording layer is installed on one of the surfaces of the
water-dispersible paper, and a water-soluble tacky adhesive layer
is installed on the opposite surface, which is being used by
attached to a returnable container and the like (Reference 3,
etc.).
[0003] As the water-dispersible paper such as water-dispersible
labels becomes used more widely, better water dispersibility has
been required than before.
REFERENCES
[0004] Reference 1: Japanese Patent Application Public Disclosure
No. H09-49188
Reference 2: Japanese Patent Application Public Disclosure No.
2000-170100
Reference 3: Japanese Patent Application Public Disclosure No.
2004-314623
Problems to be Solved by the Invention
[0005] As a result of examining the conventional water-dispersible
paper of the present applicant (References 1 and 2), it was found
that the water dispersibility is not sufficient (see Comparative
Example 5), although a water-soluble polymer (ex. carboxymethyl
cellulose salt) is used as in the present invention, because a
water-soluble polymer with high molecular weight (therefore, high
viscosity) is used in order to control the air permeability by
making the surface of the water-dispersible base material more
dense (Reference 1, [0039]) or to make the surface of the base
paper hydrophilic (Reference 2, [0017]).
[0006] Therefore, an object of the present invention is to provide
a water-dispersible sheet having further improved water
dispersibility.
Means to Solve the Problems
[0007] Carboxyalkyl cellulose derived from cellulose fiber (i.e.
pulp) includes those that retain their fibrous form without much
modification and those that is modified advancedly to become
powdery. The former is called "fibrous carboxyalkyl cellulose", and
the latter is generally called carboxyalkyl cellulose. In the
present invention, the latter is called a "carboxyalkyl cellulose
salt", which does not contain fibrous carboxyalkyl cellulose. In
both materials, those in which the carboxyalkyl group is an acid
type is water-insoluble, while those in which the carboxyalkyl
group is a salt type is water-soluble. In general, the carboxyalkyl
cellulose salt is used in applications where a thickening effect or
tacky adhesive effect is required when dissolved in water, while
the fibrous carboxyalkyl cellulose is used for the production of
water-dispersible paper together with pulps, since it has has
properties close to the property of a pulp derived from its fiber
form.
[0008] The degree of etherification of this fibrous material (i.e.
fibrous carboxyalkyl cellulose) is generally maintained low for
papermaking (ex. about 0.4 to 0.5 of degree of etherification).
Powdered material (i.e. carboxyalkyl cellulose salts) with
variously modified molecular weights (related to viscosity) and
degree of etherification is used depending on the application. For
example, a high molecular weight (hence high viscosity) is
conventionally used for a water-dispersible paper (Reference 1 and
2), while the degree of etherification has not been sufficiently
studied.
[0009] In the present invention, fibrous carboxyalkyl cellulose was
mixed with papermaking fibers to prepare a papermaking raw
material, wherein the fibrous carboxyalkyl cellulose has a low
degree of etherification so as to increase the water dispersibility
of papermaking fibers, which is favorable for papermaking, and a
carboxyalkyl cellulose salt with optimized degree of etherification
and viscosity (i.e. low viscosity) was further added to this
papermaking raw material, as a result, the water dispersibility of
the water-dispersible sheet could be greatly improved.
[0010] That is, a carboxyalkyl cellulose salt was added to the
water-dispersible sheet comprising papermaking fiber and alkalized
fibrous carboxyalkyl cellulose, then the degree of etherification
of the fibrous carboxyalkyl cellulose was set to a specific range,
and the viscosity of the carboxyalkyl cellulose salt was set to a
specific range, and further the content of the carboxyalkyl
cellulose salt was set to a specific range, then it was found that
the water dispersibility of thus prepared water-dispersible sheet
could be further improved, thereby the present invention was
completed.
[0011] That is, the present invention provides a water-dispersible
sheet comprising a papermaking fiber and an alkalized fibrous
carboxyalkyl cellulose and further comprising a carboxyalkyl
cellulose salt, wherein the degree of etherification of the fibrous
carboxyalkyl cellulose is 0.2 to 0.6, the degree of etherification
of the carboxyalkyl cellulose salt is 0.5 to 1.6, the viscosity of
1% aqueous solution of the carboxyalkyl cellulose salt measured by
Brookfield viscometer is 2 to 200 mPa-s, and the ratio of the
carboxyalkyl cellulose salt to the sum of the papermaking fibers
and the alkalized fibrous carboxyalkyl cellulose is 0.1 to 10% by
weight.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The water-dispersible sheet of the present invention
comprises a base material (hereinafter also referred to as "base
paper") and the base material comprises a papermaking fiber, an
alkalized fibrous carboxyalkyl cellulose and a carboxyalkyl
cellulose salt.
[0013] The papermaking fibers used in the present invention
includes wood pulp fibers or non-wood pulp fibers commonly used for
papermaking, for example, wood pulp fibers such as softwood Kraft
pulp, hardwood Kraft pulp, dissolving pulp, mercerized pulp;
non-wood pulp fibers such as flax pulp, Manila hemp pulp, Kenaf
pulp; purified cellulose fibers such as lyocell, and the like.
[0014] The average fiber length of the water-dispersible
papermaking fibers is 0.1 to 5 mm, preferably 0.5 to 3 mm, more
preferably 0.8 to 2 mm.
[0015] The Canadian standard freeness of the papermaking fiber is
200 to 750 ml CSF, preferably 350 to 720 ml CSF, more preferably
500 to 700 ml CSF. The Canadian standard freeness is measured
according to Japanese Industrial Standard (JIS) P8121-2 2012 (the
same shall apply hereinafter).
[0016] As the beating proceeds (the freeness decreases),
fibrillation, cutting and internal swelling of the fibers increase.
Therefore, the water dispersibility decreases, while the density,
strength and smoothness of the base paper increase.
[0017] The content of the papermaking fiber in the base paper of
the present invention is preferably 20 to 95% by weight, more
preferably 30 to 90% by weight, further preferably 40 to 80% by
weight.
[0018] The fibrous carboxyalkyl cellulose used in the present
invention is obtained by carboxyalkylation of natural cellulose
fibers, regenerated cellulose fibers or purified cellulose fibers
by a known method, and is water insoluble. The examples of the
fibrous carboxyalkyl cellulose includes fibrous carboxymethyl
cellulose, fibrous carboxyethyl cellulose and the like.
[0019] The degree of etherification (hereinafter also referred to
as "DS") of the fibrous carboxyalkyl cellulose is 0.2 to 0.6,
preferably 0.4 to less than 0.6 (i.e 0.4 or more and less than
0.6). The degree of etherification refers to the degree of
substitution of carboxyalkyl group of the fibrous carboxyalkyl
cellulose. If the degree of etherification is low, for example,
lower than 0.2, the water solubility is poor, while if the degree
of etherification is high, for example, higher than 0.6, the
sticking to the wire during papermaking of the base paper etc.
happens to make the production difficult. Therefore, in the present
invention, fibrous carboxyalkyl cellulose having such a degree of
etherification is used.
[0020] In the present invention, the fibrous carboxyalkyl cellulose
is alkalized by using an alkalizing agent. By alkalizing the base
paper, the water-insoluble fibrous carboxyalkyl cellulose in the
base paper is converted to a water-soluble fibrous carboxyalkyl
cellulose salt by a neutralization reaction, then the fibers of the
base paper tend to swell and break up in water and the base paper
becomes water dispersible.
[0021] The alkalizing agent is an aqueous solution of an alkaline
compound, and the specific examples thereof include water solutions
of alkali metal hydroxides such as sodium hydroxide and potassium
hydroxide; carbonates and bicarbonates of alkali metals such as
sodium carbonate and sodium bicarbonate; hydroxides of alkaline
earth metals such as calcium hydroxide; ammonia and ammonium salts;
amines such as ethanolamine; polyethyleneimine with a molecular
weight of 1000 or less; and the like.
[0022] The alkalization may be carried out by mixing the alkalizing
agent into a stock solution during paper making of base paper, or,
after paper making, by spraying the alkalizing agent by using a
sprayer, coating by using a coating machine, or transferring the
alkalizing agent to the paper stock by using a felt, etc. on which
the alkalizing agent is applied, and the like. It can be carried
out by any suitable method as appropriate.
[0023] The viscosity of the carboxyalkyl cellulose salt used in the
present invention is preferably in a specific range, in order to
improve the water dispersibility of the water-dispersible sheet of
the present invention (particularly, the water dispersible paper
with a tacky adhesive layer). That is, the viscosity of a 1%
aqueous solution of the carboxyalkyl cellulose salt measured by a
Brookfield viscometer is 2 to 200 mPas, preferably 2 to 100 mPas.
If this viscosity is too high, a film is formed on the surface of
the water-dispersible sheet and the water penetration becomes
worse, then the water-dispersibility is deteriorated.
[0024] The carboxyalkyl cellulose salt refers to a carboxyalkyl
cellulose in which the carboxyalkyl group is converted to a salt by
an alkali metal such as sodium or potassium.
[0025] Among these, a carboxymethyl cellulose salt is preferably
used, as the carboxyalkyl cellulose salt of the present invention,
from the viewpoint of improving water dispersibility and improving
strength.
[0026] The degree of etherification (DS) of this carboxyalkyl
cellulose salt is 0.5 to 1.6, preferably 0.6 to 1.0 (i.e. 0.6 or
more and 1.0 or less). The higher the degree of etherification of
the carboxyalkyl cellulose salt, for example, about 0.5 to 1.6, the
better the water solubility.
[0027] In the present invention, the degree of etherification of
the fibrous carboxyalkyl cellulose is preferably lower than the
degree of etherification of the carboxyalkyl cellulose salt.
[0028] The ratio of the carboxyalkyl cellulose salt to the sum of
the papermaking fibers and the alkalized fibrous carboxyalkyl
cellulose is 0.1 to 10% by weight, preferably 0.5 to 7% by weight.
If the ratio of the carboxyalkyl cellulose salt is too high, a film
is formed on the surface of the water-dispersible sheet and the
water penetration becomes worse, then the water-dispersibility is
deteriorated.
[0029] The addition of the carboxyalkyl cellulose salt may be
conducted by any suitable method as appropriate, for example, by
mixing the carboxyalkyl cellulose salt with the stock solution
during the paper making of the base paper, or by coating by using a
coating machine, or by transferring to the paper stock by using a
felt, etc.
[0030] The water-dispersible sheet of the present invention can be
produced by the following method:
[0031] (1) preparing a sheet with a papermaking raw material
comprising papermaking fibers and fibrous carboxyalkyl cellulose,
and
[0032] (2) applying an alkalinizing agent on the papermaking raw
material obtained in step (1), and (3) applying a carboxyalkyl
cellulose salt on the papermaking raw material obtained in step
(2)
[0033] or
[0034] (2 `) applying a carboxyalkyl cellulose salt on the
papermaking raw material obtained in step (1); and (3`) applying an
alkalinizing agent on the papermaking raw material obtained in the
step (2').
[0035] The steps (2) and (3) are performed simultaneously, or the
steps (2 `) and (3`) are performed simultaneously. That is, the
water-dispersible sheet of the present invention can be produced by
the following method:
[0036] (1) preparing a sheet with a papermaking raw material
comprising papermaking fibers and fibrous carboxyalkyl cellulose,
and (2'') applying a carboxyalkyl cellulose salt and an
alkalinizing agent on the papermaking raw material obtained in step
(1).
[0037] In the case of coating the alkalizing agent and/or a
carboxyalkyl cellulose salt on a base paper, the alkalizing agent
and/or a carboxyalkyl cellulose salt may be applied as an aqueous
solution of these compounds or the mixed solution of the aqueous
solution and an aqueous organic solvent compatible with the aqueous
solution, by using a coating machine, such as two-rolls coater such
as size press, transfer roll coater, air knife coater, bar coater,
spray coater, blade coater, curtain coater, champerex coater,
gravure coater or the like.
[0038] The coating amount of the alkaline compound is preferably
equal to or greater than the equivalent to neutralize the fibrous
carboxyalkyl cellulose in the base paper, more preferably 1 to 3
times the neutralization equivalent. If the amount of the alkaline
compound is less than the neutralization equivalent, water
insoluble fibrous carboxyalkyl cellulose remains, then it becomes
difficult to obtain sufficient water dispersibility, and the
solubility is greatly reduced since the carboxyalkyl celluloses are
bonded with each other over time. In addition, if the amount of the
alkaline compound exceeds 3 times the neutralization equivalent, it
is not preferable because changes in the appearance and material
occurs such as discoloration, strength reduction, etc. of the base
paper due to the influence of the alkaline compound remaining in
the base paper.
[0039] The content of the alkaline compound in the base paper
varies depending on the basic weight of the base paper, the degree
of substitution and the content of the fibrous carboxyalkyl
cellulose, the type of the alkaline compound to be used, and the
like, and is desirably appropriately adjusted. By way of example,
when the alkaline compound is sodium carbonate, the content of the
alkaline compound is 0.3 to 67% by weight based on the weight of
the base paper, and when the alkaline compound is sodium hydroxide,
the content is 2 to 51% by weight.
[0040] The basis weight of the base paper of the present invention
is usually 10 to 200 g/m.sup.2 and, in particular, the base paper
of the coated paper for printing/recording is usually 50 g/m.sup.2
or more, preferably 50 to 120 g/m.sup.2.
[0041] The water-dispersible sheet of the present invention may
have a tacky adhesive layer on one of the surfaces.
[0042] As the tacky adhesive composing the tacky adhesive layer, a
tacky adhesive having water-solubility or water re-dispersibility,
particularly a water-soluble acrylic tacky adhesive is suitably
used.
[0043] Examples of the water-soluble acrylic tacky adhesive include
those containing, as a base polymer, those comprise a copolymer
comprising alkoxyalkyl acrylate and styrene sulfonate and other
copolymerizable monomer, or a copolymer of a carboxyl
group-containing vinyl monomer such as (meth) acrylic acid and a
hydroxyl group-containing monomer and optionally other
copolymerizable monomer, and the like. Examples of the water
re-dispersible acrylic tacky adhesive include those containing, as
a base polymer, those comprise a copolymer of an alkyl (meth)
acrylate ester, a carboxyl group-containing vinyl monomer, a vinyl
monomer having an alkoxy group, and optionally other
copolymerizable monomer, or a copolymer obtained by
copolymerization of carboxylated rosin ester-containing vinyl
monomer, carboxyl group-containing vinyl monomer and water soluble
vinyl monomer, and the like. The carboxyl group of these copolymers
may be in the form of a salt in which a part or the whole thereof
is neutralized with an alkali as necessary, in which alkali metal
salts, amine salts and alkanolamine salts are preferable as the
alkali.
[0044] A crosslinking agent may be added to the water-soluble
acrylic tacky adhesive in order to adjust the adhesion strength,
water solubility or water dispersibility. Such crosslinking agent
is not particularly limited, but arbitrary ones can be
appropriately selected from those conventionally used as
crosslinking agents in acrylic tacky adhesives. Examples the
crosslinking agent include, for example, isocyanate crosslinking
agent such as 1,2-ethylene diisocyanate, epoxy type crosslinking
agent such as diglycidyl ether, melamine resins, urea resins,
dialdehydes, methylol polymers, metal chelate compounds, metal
alkoxides, metal salts and the like. A conventionally known
plasticizer, tacky adhesive, colorant, thickener, defoaming agent,
leveling agent, plasticizer, antifungal agent, antioxidant and the
like may be added to the acrylic tacky adhesive in order to adjust
the properties as necessary and to improve the performance. The
plasticizer and the tacky adhesive are preferably water-soluble or
water-dispersible. Examples of the plasticizer include polyhydric
alcohols such as sugar alcohols, polyether polyols, alkanolamine
salts of oxidized rosin, and the like. And examples of the tacky
adhesive include alkali metal salts such as rosin,
disproportionated rosin and hydrogenated rosin, ammonium salts,
polyether esters and the like.
[0045] These tacky adhesives may be (i) directly applied on the
surface of the base paper on which the alkalizing agent and/or a
carboxyalkyl cellulose salt was coated, or (ii) applied on the
release agent containing surface of the release sheet to form a
tacky adhesive layer, which is then adhered to the surface of the
base paper on which the alkalizing agent and/or a carboxyalkyl
cellulose salt was coated to transfer the adhesive layer to the
surface of the base paper. In either case, a release sheet may be
pasted on the adhesive layer and peeled off at the time of use as
desired, in order to prevent unnecessary adhesion at times other
than use. The coating amount (solid content) of the tacky adhesive
layer formed is about 3 to 60 g/m.sup.2, preferably about 10 to 50
g/m.sup.2. When the tacky adhesive coating amount is less than 5
g/m.sup.2, the formed tacky adhesive sheet is insufficient in tacky
adhesiveness. On the other hand, when the tacky adhesive coating
amount exceeds 60 g/m.sup.2, the tacky adhesive easily protrudes
during production of the tacky adhesive sheet or in a
post-processing step, which is not preferable.
[0046] The release sheet is not particularly limited and
conventionally known release sheet may be used, for example, paper
base materials such as glassine paper, coated paper, cast coated
paper; laminated paper obtained by laminating thermoplastic resins
such as polyethylene etc. on these base paper materials; or various
plastic films such as polyethylene terephthalate, polypropylene,
polyethylene and the like, on whose one side or both sides release
agent such as silicone resin are applied. The basic weight of the
release sheet is not particularly limited, but it is usually about
20 to 120 g/m.sup.2.
[0047] The application of the tacky adhesive may be carried out by
a printing method and the tacky adhesive may be applied in a
pattern shape excluding an edge portion and the like. And the
release sheet used in this case may also be partially coated with a
release agent corresponding to the pattern shape of the tacky
adhesive. Furthermore, a release agent is partially applied on one
side of the water-dispersible sheet of the present invention in a
dot-like or rectangular discontinuous pattern, while the tacky
adhesive is partially applied in a pattern corresponding to the
pattern of the release agent on the surface opposite to the surface
on which the release agent is applied, then the adhesive applied
surface and the release agent applied surface are overlapped to be
able to prepare a tacky adhesive sheet that does not require a
release sheet.
[0048] Arbitrary coating layers such as aqueous coating layer,
thermosensitive recording layer or inkjet recording layer may be
installed on the other side of the water-dispersible sheet of the
present invention, opposite to the tacky adhesive layer, depending
on the application.
[0049] The coating layer in the present invention may be a single
layer or a multilayer as long as it is formed by coating and drying
aqueous coating materials, and the coating method is not limited.
In addition, the components of the coating layer may be
appropriately chosen from those suitable for the coating or
printing method (offset printing, gravure printing, inkjet printer,
thermal printer, laser beam printer, etc.).
[0050] Examples of the coating layers suitable for thermal
printers, inkjet printers, and gravure printing are shown
below.
[0051] (I) Example of Coating Layer (Thermosensitive Recording
Layer) Suitable for Thermal Printers:
[0052] In order to adapt the water-dispersible sheet of the present
invention to printing with a thermal printer, a thermosensitive
recording layer containing, as main components, a colorless or pale
electron donating leuco dye (henceforth referred to as "leuco dye")
and an electron accepting color developing agent (henceforth
referred to as "color development agent") is installed on the other
side of the water-dispersible sheet, opposite to the tacky adhesive
layer. An undercoat coating layer comprising a pigment and a binder
as main components may be installed between the base paper and the
thermosensitive recording layer. Since the base paper has a porous
layer (with high heat insulating effect) containing fibrous
carboxyalkyl cellulose, the debris forming and the sticking
properties are improved.
[0053] The smoothness of the surface of the base paper on which the
undercoat layer is installed is not particularly limited, but in
general, a highly smooth surface is preferred, and a Yankee dryer
contacted surface and a calendaring treated surface are suitably
used.
[0054] The undercoat layer is installed to enhance the smoothness
of the surface of the base paper and achieve sharpness and high
sensitivity of the image in the thermosensitive recording medium.
Any known pigments, binders and various additives are properly
selected to be used for the undercoat layer. It is preferable to
install the undercoat layer, because, without the undercoat layer,
the thermosensitive recording layer contacts directly with the base
paper containing the alkalizing agent and/or the carboxyalkyl
cellulose salt then the coloring sensitivity of the thermosensitive
recording layer may be lowered.
[0055] As the pigment for the undercoat layer, inorganic pigments
such as silica, calcium carbonate, clay, kaolin, calcined kaolin,
diatomaceous earth, talc, titanium oxide, aluminum hydroxide,
magnesium carbonate, zinc oxide, aluminum oxide, magnesium
hydroxide, barium sulfate, calcium sulfate, zinc sulfate, calcium
silicate, aluminum silicate, magnesium silicate, sodium
aluminosilicate and magnesium aluminosilicate and the like, or
organic pigments such as melamine resin pigment, urea-formalin
resin pigment, polyethylene powder, nylon powder and the like may
be mentioned.
[0056] As the binder of the undercoat layer, water-soluble resins
and water-dispersible resins are preferable, the example include
starches, hydroxyethyl cellulose, methylcellulose, carboxymethyl
cellulose salt, gelatin, casein, sodium alginate, polyvinyl
alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone,
polyacrylamide, acrylamide/acrylate copolymer, styrene/maleic
anhydride copolymer and alkali salt thereof, ethylene/maleic
anhydride copolymer and alkali salt thereof, sodium polyacrylate
and the like. Among them, from the viewpoint of water
dispersibility, it is desirable to use water-soluble resins such as
starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl
cellulose salt, gelatin, casein, sodium alginate, polyvinyl
alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone as the
main component of the binder.
[0057] The amount (solid content) of the binder in the undercoat
layer is usually 5 to 100 parts by weight per 100 parts by weight
of the pigment.
[0058] In addition to the pigment and the binder, commonly used
various additives may be used for the undercoat layer. Examples of
the various additives include pigment dispersants, defoaming
agents, lubricants, UV absorbers, sizing agents, sensitizers,
fluorescent dyes, preservatives, and the like.
[0059] The undercoat layer may be obtained by applying the coating
material obtained by dispersing and mixing the pigment and the
binder with other additives in one layer or multi-layers by using a
coating machine then drying by heating it by using a dryer or the
like.
[0060] The coating amount (solid content) of the undercoat layer is
usually 0.5 to 50 g/m.sup.2, preferably 3 to 15 g/m.sup.2. Examples
of the coating machine include air knife coater, bar coater, roll
coater, blade coater, curtain coater, champlex coater, gravure
coater etc.
[0061] As the leuco dyes used for the thermosensitive recording
layer of the present invention, any known leuco dyes can be used
solely or in combination of two or more, and in particular, leuco
compounds of dye such as triphenylmethane type, fluoran type,
phenothiazine type, auramine type, spiropyran type,
indolinophthalide type and the like are preferably used. Examples
of the leuco dyes include 3,3-bis(p-Dimethyl
aminophenyl)-phthalide, 3,3-bis(p-Dimethyl
aminophenyl)-6-dimethylaminophthalide [alternate name: crystal
violet lactone], 3,3-bis(p-Dimethyl
aminophenyl)-6-diethylaminophthalide, 3,3-bis(p-Dimethyl
aminophenyl)-6-chlorophthalide, 3,3-bis(p-Dibuthyl
aminophenyl)-phthalide, 3-cyclohexylamino-6-chlorofluoran,
3-dimethylamino-5,7-dimethylfluoran,
3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran,
3-diethylamino-7,8-benzfluorane,
3-diethylamino-6-methyl-7-chlorofluoran,
3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluoran,
3-pyrrolidino-6-methyl-7-anilinofluoran,
2-{N-(3'-trifluoromethylphenyl) amino}-6-diethylaminofluoran,
2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xanthylbenzoic acid
lactam}, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)
fluoran, 3-diethylamino-7-(o-chloroanilino) fluoran,
3-di-n-butylamino-7-(o-chloroanilino) fluoran, 3-N-methyl-N,
n-amylamino-6-methyl-7-anilinofluoran,
3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7-anilinofluoran, 3-(N,
N-diethylamino)-5-methyl-7-(N, N-dibenzylamino) fluoran, Benzoyl
leuco methylene blue,
6'-chloro-8'-methoxy-benzoindolino-spiropyran,
6'-bromo-3'-methoxy-benzoindolino-spiropyran,
3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)
phthalide,
3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)
phthalide,
3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)
phthalide,
3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'-methylph-
enyl) phthalide, 3-(N-ethyl-N-tetrahydrofurfuryl)
amino-6-methyl-7-anilinofluoran, 3-N-ethyl-N-(2-ethoxypropyl)
amino-6-methyl-7-anilinofluoran,
3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran,
3-morpholino-7-(N-propyl-trifluoromethylanilino) fluoran,
[0062] 3-pyrrolidino-7-m-trifluoromethylanilinofluoran,
3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)
fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl) methylaminofluoran,
3-diethylamino-5-chloro-7-(.alpha.-phenylethylamino) fluoran,
3-(N-ethyl-p-toluidino)-7-(.alpha.-phenylethylamino) fluoran,
3-diethylamino-7-(o-methoxycarbonylphenylamino) fluoran,
3-diethylamino-5-methyl-7-(.alpha.-phenylethylamino) fluoran,
3-diethylamino-7-piperidinofluoran,
2-chloro-3-(N-methyltoluidino)-7-(p-n-butylanilino) fluoran,
3-(N-methyl-N-isopropylamino)-6-methyl-7-anilinofluoran,
3-di-n-butylamino-6-methyl-7-anilinofluoran, 3,6-bis(dimethylamino)
fluorene spiro (9,3')-6'-dimethylaminophthalide,
3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-.alpha.-naphthylamino-4'-bromo-
fluoran, 3-diethylamino-6-chloro-7-anilinofluoran,
3-diethylamino-6-methyl-7-mesityzino-4',5'-benzofluoran,
3-N-methyl-N-isopropyl-6-methyl-7-anilinofluoran,
3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran,
3-Diethylamino-6-methyl-7-(2', 4'-dimethylanilino) fluoran, and the
like.
[0063] The water-dispersible sheet of the present invention are
possibly used in an application to be washed away to a drainage
groove after use, therefore, among these, preferably used are leuco
dyes with higher safety from the viewpoint of environment, such as
3-diethylamino-6-methyl-7-anilinofluoran,
3-dibutylamino-6-methyl-7-anilinofluoran,
3-(N-cyclohexyl-N-methylamino)-6-methyl-7-anilinofluoran,
3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran,
3-N-di-n-pentylamino-6-methyl-7-anilinofluoran,
3-diethylamino-7-(3-trifluoromethylanilino) fluoran,
3-(N-ethyl-N-4-methylphenylamino)-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7-(3-methylanilino) fluoran, 3,3'-bis
(dimethylaminophenyl)-6-dimethylaminophthalide,
3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azapht-
halide, 2-(N-phenyl-N-methylamino)-6-(N-p-tolyl-N-ethylamino)
fluoran, 3,3-bis(1-n-butyl-2-methyl-indol-3-yl) phthalide,
1,3-dimethyl-6-diethylaminofluoran,
3-Bromo-3-methyl-6-dibutylaminofluoran, and the like.
[0064] As the color developing agent contained in the
thermosensitive recording layer together with the leuco dye,
phenols, organic acids or inorganic acids or their esters, salts
and the like may be used. Example of the color developing agent
include gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid,
3,5-di-.alpha.-methylbenzylsalicylic acid,
4,4'-isopropylidenediphenol,
1,1'-isopropylidenebis(2-chlorophenol), 4,4'-isopropylin
bis(2,6-dibromophenol), 4,4'-isopropylidenebis(2,6-dichlorophenol),
4,4'-isopropylidenebis(2-methylphenol),
4,4'-isopropylidenebis(2,6-dimethylphenol),
4,4-isopropylidenebis(2-tert-butylphenol),
4,4'-sec-butylidenediphenol, 4,4'-cyclohexylidene bisphenol,
4,4'-cyclohexylidene bis(2-methylphenol), 4-tert-butylphenol,
4-phenylphenol, 4-hydroxydiphenoxide, .alpha.-naphthol, 6-naphthol,
3,5-xylenol, thymol, methyl-4-hydroxybenzoate,
4-hydroxyacetophenone, novolac type phenolic resin,
2,2'-thiobis(4,6-dichlorophenol), catechol, resorcin, hydroquinone,
pyrogallol, fluoroglycine, fluoroglycine carboxylic acid,
4-tert-octyl catechol, 2,2'-methylenebis(4-chlorophenol),
2,2'-methylenebis(4-methyl-6-tert-butylphenol),
2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl
p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl
p-hydroxybenzoate, p-hydroxybenzoic acid-p-chlorobenzyl,
p-hydroxybenzoic acid-o-chlorobenzyl, p-hydroxybenzoic
acid-p-methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid,
zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic
acid, zinc 2-hydroxy-6-naphthoate, 4-hydroxydiphenyl sulfone,
4-hydroxy-4'-chlorodiphenyl sulfone, bis(4-hydroxyphenyl)
sulfide,
[0065] 2-hydroxy-p-toluic acid, zinc 3,5-di-tert-butylsalicylate,
3,5-di-tert-butyl salicylate, tartaric acid, oxalic acid, maleic
acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic
acid, boric acid, thiourea derivatives, 4-hydroxythiophenol
derivatives, bis(4-hydroxyphenyl) acetic acid, ethyl
bis(4-hydroxyphenyl) acetate, N-propyl bis(4-hydroxyphenyl)
acetate, N-butyl bis(4-hydroxyphenyl) acetate, phenyl
bis(4-hydroxyphenyl) acetate, bis(4-hydroxyphenyl) acetate benzyl,
phenethyl bis(4-hydroxyphenyl) acetate,
bis(3-methyl-4-hydroxyphenyl) acetic acid, methyl
bis(3-methyl-4-hydroxyphenyl) acetate, N-propyl
bis(3-methyl-4-hydroxyphenyl) acetate, 1,7-bis(4-hydroxyphenylthio)
3,5-dioxaheptane, 1,5-bis(4-hydroxyphenylthio) 3-oxapentane,
dimethyl 4-hydroxyphthalate, 4-hydroxy- 4'-methoxydiphenyl sulfone,
4-hydroxy-4'-ethoxydiphenyl sulfone, 4-hydroxy-4'-isopropoxy
diphenyl sulfone, 4-hydroxy-4'-propoxy diphenyl sulfone,
4-hydroxy-4'-butoxydiphenyl sulfone, 4-hydroxy-4'-isobutoxydiphenyl
sulfone, 4-hydroxy-4'-sec-butoxydiphenyl sulfone,
4-hydroxy-4'-tert-butoxydiphenyl sulfone, 4-hydroxy-4'-benzyloxy
diphenyl sulfone, 4-hydroxy-4'-phenoxydiphenyl sulfone,
4-hydroxy-4'-(m-methylbenzyloxy) diphenyl sulfone,
4-hydroxy-4'-(p-methylbenzyloxy) diphenyl sulfone,
4-hydroxy-4'-(o-methylbenzyloxy) diphenyl sulfone,
4-hydroxy-4'-(p-chlorobenzyloxy) diphenylsulfone and the like.
[0066] The water-dispersible sheet of the present invention are
possibly used in an application to be washed away to a drainage
groove after use, therefore, among these, preferably used are color
developing agents with higher safety from the viewpoint of
environment, such as 4,4'-dihydroxydiphenyl sulfone,
2,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropoxy diphenyl
sulfone, benzyl parahydroxybenzoate, 4-hydroxy-4'-propoxy diphenyl
sulfone, 3-{[(phenylamino) carbonyl] amino} benzenesulfonamide,
N-(4'-hydroxyphenylthio) acetyl-2-hydroxyaniline, 1:1 mixture of
N-(4'-hydroxyphenylthio) acetyl-4-hydroxyaniline and
N-(4'-hydroxyphenylthio) acetyl-2-hydroxyaniline,
4,4'-bis(3-(phenoxycarbonylamino) methylphenylureido) diphenyl
sulfone, composition of color developing agents containing 2,2'-bis
[4-(4-hydroxyphenylsulfone) phenoxy] diphenyl ether, and the
like.
[0067] Any known binders can be used for the thermosensitive
recording layer. Examples of the main ingredient of the binder
include polyvinyl alcohols such as fully saponified polyvinyl
alcohol and partially saponified polyvinyl alcohol; modified
polyvinyl alcohols such as carboxy-modified polyvinyl alcohol,
amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl
alcohol, butyral-modified polyvinyl alcohol, and other modified
polyvinyl alcohol; water-soluble resin such as hydroxyethyl
cellulose, methyl cellulose, carboxymethyl cellulose salt,
starches, gelatin, casein, sodium alginate, polyvinyl pyrrolidone,
polyacrylamide, acrylamide/acrylate copolymer, alkali salt of
styrene/maleic anhydride copolymer, alkali salt of ethylene/maleic
anhydride copolymer; water dispersible resins such as
styrene-butadiene copolymer, acrylonitrile/butadiene copolymer,
methyl acrylate/butadiene copolymer,
acrylonitrile/butadiene/styrene terpolymer, cellulose derivatives
such as ethyl cellulose, acetyl cellulose, polyvinyl chloride,
polyvinyl acetate, vinyl acetate/acrylic acid ester copolymer,
ethylene/vinyl acetate copolymer, polyacrylic esters,
styrene/acrylate copolymer, polyurethane resin, polyvinyl butyral
polystyrene and copolymers thereof, polyamide resin, silicone
resin, petroleum resin, terpene resin, ketone resin, coumarone
resin. These may be used by being dissolved into a solvent such as
water, alcohol, ketone, ester, hydrocarbon, etc. These also may be
used in a state of being emulsified or paste dispersed in water or
other medium, and these may also be used in combination depending
on the required quality. Among these, water-soluble resins are
preferably used as the main ingredient of the binder from the
viewpoint of water dispersibility, such as starches, hydroxyethyl
cellulose, methyl cellulose, carboxymethyl cellulose salt, gelatin,
casein, sodium alginate, polyvinyl alcohols, modified polyvinyl
alcohols, and polyvinylpyrrolidone.
[0068] In the thermosensitive recording layer, auxiliary additives
may be used together with the leuco dye, the color developing agent
and the binder, if necessary. Examples of the auxiliary additives
include sensitizers, pigments, stabilizers such as p-nitrobenzoic
acid metal salt (Ca, Zn) or phthalic acid monobenzyl ester metal
salt (Ca, Zn), releasing agents such as fatty acid metal salt,
lubricants such as waxes, pressure coloring preventing agents,
benzophenone and triazole UV absorbers, waterproofing agents such
as glyoxal, dispersing agents, antifoaming agents, etc.
[0069] Thermoplastic materials are used as a sensitizer to improve
the thermal responsiveness, and a thermoplastic organic compound
with a melting point of about 50 to 200 degree C. may be used.
Examples of such thermoplastic organic compound include stearic
acid amide, palmitic acid amide, N-hydroxymethylstearic acid amide,
N-stearyl stearic acid amide, ethylene bis stearic acid amide,
N-stearyl urea, benzyl-2-naphthyl ether, m-terphenyl,
4-benzylbiphenyl, 2,2'-bis(4-methoxyphenoxy) diethyl ether,
.alpha., .alpha.'-diphenoxyxylene, bis(4-methoxyphenyl) ether,
diphenyl adipate, dibenzyl oxalate, di (4-chlorobenzyl) oxalate,
dimethyl terephthalate, dibenzyl terephthalate, benzenesulfonic
acid phenyl ester, bis(4-allyloxyphenyl) sulfone,
4-acetylacetophenone, acetoacetic acid anilides, fatty acid
anilides, montan wax, polyethylene wax, benzyl p-benzyloxybenzoate,
di-p-tolyl carbonate, phenyl-.alpha.-naphthyl carbonate,
1,4-diethoxynaphthalene, 1-hydroxy-2-naphthoic acid phenyl ester,
1,2-bis-(3-methylphenoxy) ethane, di (p-methylbenzyl) oxalate,
1,2-bis (phenoxymethyl) benzene, diphenyl sulfone, para phenyl
acetophenone, -benzyloxynaphthalene, 4-biphenyl-p-tolyl ether,
o-xylerine-bis-(phenyl ether), 4-(m-methylphenoxymethyl) biphenyl
and the like.
[0070] The water-dispersible sheet of the present invention are
possibly used in an application to be washed away to a drainage
groove after use, therefore, among these, preferably used are
sensitizers with higher safety from the viewpoint of environment,
such as stearic acid amide, palmitic acid amide, ethylene bis
stearic acid amide, benzyl p-benzyloxybenzoate, 4-biphenyl-p-tolyl
ether, di (p-methylbenzyl) oxalate, di (4-chlorobenzyl) oxalate,
4-benzylbiphenyl, 1,2-bis (phenoxymethyl) benzene, diphenyl
sulfone, -benzyloxynaphthalene, paraphenylacetophenone,
1,2-bis-(3-methylphenoxy) ethane, and the like.
[0071] Examples of the pigments include inorganic filler, such as
silica, calcium carbonate, clay, kaolin, calcined kaolin,
diatomaceous earth, talc, titanium oxide, aluminum hydroxide,
magnesium carbonate, zinc oxide, aluminum oxide, magnesium
hydroxide, barium sulfate, calcium sulfate, zinc sulfate, calcium
silicate, aluminum silicate, magnesium silicate, sodium
aluminosilicate, magnesium aluminosilicate and the like; or organic
pigments, such as melamine resin pigment, urea-formalin resin
pigment, polyethylene powder, nylon powder and the like.
[0072] The types and amounts of the leuco dye, color developing
agent, sensitizer and other various ingredients are determined
according to the required performance and printability and are not
particularly restricted. However, from 0.5 parts to 10 parts of the
color developing agent and from 0.5 parts to 10 parts of the
sensitizer are ordinarily used per 1 part of the leuco dye, and the
amount of the binder is suitably 5 to 50% by weight in the total
solid content.
[0073] The leuco dye, the color developing agent and the materials
added when needed are finely ground into particles, several microns
or smaller in size, using a grinder or a suitable emulsification
device such as a ball mill, attritor, sand grinder and the like,
and a coating solution is prepared by adding a binder and various
additive materials depending on the objective.
[0074] The method for forming the thermosensitive recording layer
is not limited in particular, and the layer is formed by, for
example, coating and drying the coating material on the base paper
by a method such as various printing methods such as planographic
printing, or air knife coating, rod blade coating, bar coating,
blade coating, gravure coating, curtain coating and the like. The
coating amount of the thermosensitive recording layer is usually in
the range of from 2 to 12 g/m.sup.2, preferably from 3 to 10
g/m.sup.2.
[0075] Also, the matching property with the thermal head or the
like and the storage image storage property can be improved by
optionally installing a protective layer on the thermosensitive
recording layer.
[0076] As the binder used for the protective layer, the same type
as the binder used for thermosensitive recording layer may be used.
Examples of the main ingredient of the binder include polyvinyl
alcohols such as fully saponified polyvinyl alcohol and partially
saponified polyvinyl alcohol; modified polyvinyl alcohols such as
carboxy-modified polyvinyl alcohol, amide-modified polyvinyl
alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified
polyvinyl alcohol, and other modified polyvinyl alcohol;
water-soluble resin such as hydroxyethyl cellulose, methyl
cellulose, carboxymethyl cellulose salt, starches, gelatin, casein,
sodium alginate, polyvinyl pyrrolidone, polyacrylamide,
acrylamide/acrylate copolymer, alkali salt of styrene/maleic
anhydride copolymer, alkali salt of ethylene/maleic anhydride
copolymer; water dispersible resins such as styrene-butadiene
copolymer, acrylonitrile/butadiene copolymer, methyl
acrylate/butadiene copolymer, acrylonitrile/butadiene/styrene
terpolymer, cellulose derivatives such as ethyl cellulose, acetyl
cellulose, polyvinyl chloride, polyvinyl acetate, vinyl
acetate/acrylic acid ester copolymer, ethylene/vinyl acetate
copolymer, polyacrylic esters, styrene/acrylate copolymer,
polyurethane resin, polyvinyl butyral polystyrene and copolymers
thereof, polyamide resin, silicone resin, petroleum resin, terpene
resin, ketone resin, coumarone resin. These may be used by being
dissolved into a solvent such as water, alcohol, ketone, ester,
hydrocarbon, etc. These also may be used in a state of being
emulsified or paste dispersed in water or other medium, and these
may also be used in combination depending on the required quality.
Among these, water-soluble resins are preferably used as the main
ingredient of the binder from the viewpoint of water
dispersibility, such as starches, hydroxyethyl cellulose, methyl
cellulose, carboxymethyl cellulose salt, gelatin, casein, sodium
alginate, polyvinyl alcohols, modified polyvinyl alcohols, and
polyvinylpyrrolidone.
[0077] Examples of the additives used for the protective layer
include pigments, surfactants, lubricants, pressure coloring
inhibitors, and the like. The specific examples of the pigment and
the lubricant are the same as those exemplified in the
thermosensitive recording layer. The protective layer is obtained
by preparing the coating material by dispersing and mixing various
additives in the binder, applying the coating material in one or
more layers by a coating machine and drying it by heating with a
dryer.
[0078] The coating amount (solid content) of the protective layer
is usually 0.2 to 10 g/m.sup.2, preferably 0.5 to 5 g/m.sup.2. The
coating machine is not particularly limited, and known coating
machines can be used such as air knife coater, bar coater, roll
coater, blade coater, curtain coater, champlex coater, gravure
coater and the like.
[0079] In the present invention, it is preferable to increase the
surface smoothness of the thermosensitive recording layer side of
the water-dispersible sheet in order to improve the image sharpness
and sensitivity by using a smoothing device such as calendar, super
calendar, soft nip calender or the like.
[0080] The Bekk smoothness on the surface of the thermosensitive
recording layer side is preferably 50 to 2000 seconds, more
preferably 100 to 2000 seconds. If the Bekk smoothness is less than
50 seconds, the effect of improving the image sharpness and
sensitivity may be poor. Also, if the Bekk smoothness exceeds 2000
seconds, a decrease in water dispersibility may become apparent due
to the increase in the density of the base paper, which is not
preferable.
[0081] (II) Example of Coating Layer Suitable for Inkjet Printers
(Inkjet Recording Layer):
[0082] In order to adapt the water-dispersible sheet of the present
invention to printing with an inkjet printer, it is preferable to
install, on the other side of the water-dispersible sheet, opposite
to the tacky adhesive layer, a pigment coating layer comprising a
pigment and an aqueous binder as main components or a clear coat
layer comprising a cationic resin and/or an aqueous binder as main
components. The pigment, binder and various additives may be
selected appropriately from any known pigments, binders and various
additives and used, and the compounding amounts of these may be
appropriately adjusted according to the required quality. In
addition, since the base paper contains a porous layer (having high
ink absorbability) comprising fibrous carboxyalkyl cellulose, it
has an improved ink absorbability.
[0083] Examples of the pigments include inorganic pigments such as
silica, colloidal silica, calcium carbonate, clay, kaolin, calcined
kaolin, diatomaceous earth, talc, titanium oxide, aluminum
hydroxide, magnesium carbonate, zinc oxide, aluminum oxide,
magnesium hydroxide, barium sulfate, calcium sulfate, zinc sulfate,
calcium silicate, aluminum silicate, magnesium silicate, sodium
aluminosilicate, magnesium aluminosilicate, calcium carbonate
complex silica; or organic pigments such as melamine resin pigment,
urea-formalin resin pigment, polyethylene powder, nylon powder,
styrene, styrene-acryl, acryl. Among these, silica, alumina,
calcined kaolin, calcium carbonate or the like are preferably used
from the viewpoints of ink absorbability and coloring property.
[0084] As the binder, water-soluble resins and water-dispersible
resins are preferred, such as starch, hydroxyethyl cellulose,
methyl cellulose, carboxymethyl cellulose salt, gelatin, casein,
sodium alginate, polyvinyl alcohol, modified polyvinyl alcohol,
polyvinyl pyrrolidone, polyacrylamide, acrylamide/acrylate
copolymer, styrene/maleic anhydride copolymer and its alkali salt,
ethylene/maleic anhydride copolymer and its alkali salt,
styrene/butadiene copolymer, sodium polyacrylate, vinyl acetate,
ethylene-vinyl acetate, acrylic acid copolymer, methacrylic acid
copolymer, acrylic acid/methacrylic acid copolymer and the like.
Among these, polyvinyl alcohol, modified polyvinyl alcohol, or the
like are preferably used from the viewpoints of ink absorbability
and coloring property.
[0085] Examples of the additives include cationic resins (dye
fixing agents), pigment dispersants, defoaming agents, lubricants,
UV absorbers, sizing agents, fluorescent dyes, preservatives, and
the like. Among these, cationic resin is preferably used in
combination because it significantly improves the water resistance
and color development of the image area.
[0086] The coating machine is not particularly limited, and air
knife coater, bar coater, roll coater, blade coater, curtain
coater, cast coater, champlex coater, gravure coater, two rolls
coater, transfer roll coater, and the like may be used.
[0087] (III) Example of Coating Layer Suitable for Gravure
Printing:
[0088] In order to adapt the water-dispersible sheet of the present
invention to gravure printing, it is preferable to install, on the
other side of the water-dispersible sheet, opposite to the tacky
adhesive layer, a pigment coating layer comprising a pigment and an
aqueous binder as main components or a clear coat layer comprising
an aqueous binder as main components. The pigment, binder and
various additives may be selected appropriately from any known
pigments, binders and various additives and used. In addition,
since the base paper contains a porous layer (having high
cushioning property) comprising fibrous carboxyalkyl cellulose, it
has an improved ink adherence.
[0089] Examples of the pigments include inorganic pigment such as
calcium carbonate, clay, kaolin, calcined kaolin, diatomaceous
earth, talc, titanium oxide, aluminum hydroxide, magnesium
carbonate, zinc oxide, aluminum oxide, magnesium hydroxide, barium
sulfate, calcium sulfate, zinc sulfate, calcium silicate, aluminum
silicate, magnesium silicate, sodium aluminosilicate, magnesium
aluminosilicate, silica, colloidal silica, calcium carbonate
composite silica and the like; or organic pigment such as melamine
resin pigment, urea-formalin resin pigment, polyethylene powder,
nylon powder, styrene, styrene-acryl, acryl and the like.
[0090] As the binder, water-soluble resins and water-dispersible
resins are preferred, such as starch, hydroxyethyl cellulose,
methyl cellulose, carboxymethyl cellulose salt, gelatin, casein,
sodium alginate, polyvinyl alcohol, modified polyvinyl alcohol,
polyvinyl pyrrolidone, polyacrylamide, acrylamide/acrylate
copolymer, styrene/maleic anhydride copolymer and its alkali salt,
ethylene/maleic anhydride copolymer and its alkali salt,
styrene/butadiene copolymer, sodium polyacrylate, vinyl acetate,
ethylene-vinyl acetate, acrylic acid copolymer, methacrylic acid
copolymer, acrylic acid/methacrylic acid copolymer and the like.
Among these, from the viewpoint of water dispersibility, preferred
binders are water-soluble resins such as starch, hydroxyethyl
cellulose, methyl cellulose, carboxymethyl cellulose salt, gelatin,
casein, sodium alginate, polyvinyl alcohol, modified polyvinyl
alcohol, polyvinyl pyrrolidone.
[0091] Examples of the additives include cationic resins (dye
fixing agents), pigment dispersants, defoaming agents, lubricants,
UV absorbers, sizing agents, fluorescent dyes, preservatives, and
the like.
[0092] The coating machine is not particularly limited, and air
knife coater, bar coater, roll coater, blade coater, curtain
coater, cast coater, champlex coater, gravure coater, two rolls
coater, transfer roll coater, and the like may be used.
[0093] The water-dispersible sheet of the present invention thus
obtained can, after it is adhered to a substrate such as a
container or a returnable container, be easily removed from the
substrate only by being rinsed off with water.
EXAMPLES
[0094] The following Examples illustrate the present invention, but
the Examples are not intended to limit the scope of the present
invention.
Example 1
[0095] A hand-made paper of a single layer sheet (basic weight: 54
g/m.sup.2) (hereinafter also referred to as "pulp sheet") was
prepared using a papermaking material, which comprises 80% by
weight of hardwood bleached kraft pulp beaten to 550 ml CSF of
Canadian standard freeness as a papermaking pulp and 20% by weight
of a fibrous carboxymethyl cellulose (hereinafter referred to as
"fibrous CMC", Degree of etherification (DS) is 0.43). Then a
water-dispersible sheet was prepared by applying an aqueous
solution of sodium carbonate (soda ash light manufactured by
Tokuyama Corporation) as an alkalizing agent and carboxymethyl
cellulose sodium salt powder (hereinafter referred to as "CMC-Na
salt", trade name: Sunrose, manufactured by Nippon Paper Industries
Co., Ltd., Degree of etherification (DS) of 0.7, viscosity of 3
mPa-s as 1% by weight aqueous solution at 20 degree C.) on the
hand-made paper by a size press method, so that the amount of the
sodium carbonate with respect to the hand-made paper is 8.0 wt %
(the amount of the sodium carbonate on the hand-made paper is 4.3
g/m.sup.2) and the amount of the carboxymethyl cellulose sodium
salt with respect to the hand-made paper is 3.1 wt % (the amount of
the carboxymethyl cellulose sodium salt on the hand-made paper is
1.7 g/m.sup.2).
Example 2
[0096] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of beating the hardwood bleached
kraft pulp up to Canadian standard freeness of 650 mL CSF.
Example 3
[0097] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of beating the hardwood bleached
kraft pulp up to Canadian standard freeness of 450 mL CSF.
Example 4
[0098] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of applying an aqueous solution of
the sodium carbonate and carboxymethyl cellulose sodium salt (trade
name: Sunrose, manufactured by Nippon Paper Industries Co., Ltd.,
Degree of etherification (DS) of 0.9, viscosity of 28 mPa-s as 1%
by weight aqueous solution at 20 degree C.) on the hand-made paper
by a size press method, so that the amount of the sodium carbonate
with respect to the hand-made paper is 8.0 wt % and the amount of
the carboxymethyl cellulose sodium salt with respect to the
hand-made paper is 3.1 wt %.
Example 5
[0099] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of applying an aqueous solution of
the sodium carbonate and carboxymethyl cellulose sodium salt (trade
name: Sunrose, manufactured by Nippon Paper Industries Co., Ltd.,
Degree of etherification (DS) of 0.7, viscosity of 170 mPa-s as 1%
by weight aqueous solution at 20 degree C.) on the hand-made paper
by a size press method, so that the amount of the sodium carbonate
with respect to the hand-made paper is 8.0 wt % and the amount of
the carboxymethyl cellulose sodium salt with respect to the
hand-made paper is 3.1 wt %.
Example 6
[0100] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of applying an aqueous solution of
the sodium carbonate and the carboxymethyl cellulose sodium salt on
the hand-made paper by a size press method, so that the amount of
the sodium carbonate with respect to the hand-made paper is 9.3 wt
% (the amount of the sodium carbonate on the hand-made paper is 5.0
g/m.sup.2) and the amount of the carboxymethyl cellulose sodium
salt with respect to the hand-made paper is 1.9 wt % (the amount of
the carboxymethyl cellulose sodium salt on the hand-made paper is
1.0 g/m.sup.2).
Example 7
[0101] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of preparing a hand-made paper of a
single layer sheet (basic weight: 54 g/m.sup.2) by using a
papermaking material, which comprises 50% by weight of the hardwood
bleached kraft pulp and 50% by weight of the fibrous carboxymethyl
cellulose (Degree of etherification (DS) is 0.43).
Example 8
[0102] A hand-made paper of a single layer sheet (basic weight: 54
g/m.sup.2) was prepared using a papermaking material, which
comprises 70% by weight of hardwood bleached kraft pulp beaten to
250 ml CSF of Canadian standard freeness and 30% by weight of a
fibrous carboxymethyl cellulose (Degree of etherification (DS) is
0.43). Then a water-dispersible sheet was prepared in the same
manner as in Example 1 with the exception of applying an aqueous
solution of the sodium carbonate and the carboxymethyl cellulose
sodium salt on the hand-made paper by a size press method, so that
the amount of the sodium carbonate with respect to the hand-made
paper is 10.5 wt % (the amount of the sodium carbonate on the
hand-made paper is 5.5 g/m.sup.2) and the amount of the
carboxymethyl cellulose sodium salt with respect to the hand-made
paper is 4.2 wt % (the amount of the carboxymethyl cellulose sodium
salt on the hand-made paper is 2.2 g/m.sup.2).
Example 9
[0103] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of preparing a hand-made paper of a
single layer sheet (basic weight: 54 g/m.sup.2) by using a
papermaking material, which comprises 95% by weight of hardwood
bleached kraft pulp beaten to 650 ml CSF of Canadian standard
freeness and 5% by weight of a fibrous carboxymethyl cellulose
(Degree of etherification (DS) is 0.43).
Example 10
[0104] A tacky adhesive coating solution with the following
formulation was prepared. Then this tacky adhesive was applied on a
release treatment surface of a commercially available release sheet
coated with a silicone release agent with a solid weight of 25
g/m.sup.2 and dried to prepare a release sheet on which an adhesive
layer was formed.
<Tacky Adhesive Coating Solution>
TABLE-US-00001 [0105] Water-soluble acrylic adhesive (VIGteQnos
Co., 100 parts Ltd., trade name "Riki-Dyne AR-2410", solid content
42 wt %) Crosslinking agent (VIGteQnos Co., Ltd., 0.1 parts trade
name "Sunpasta HD-5013")
[0106] This tacky adhesive layer on the release sheet was then
adhered to the water-dispersible sheet prepared in Example 1 to
prepare a water-dispersible sheet.
Example 11
[0107] The color development agent dispersion (solution A), the
leuco dye dispersion (solution B) and the sensitizer dispersion
(solution C) with the following formulations were separately wet
ground using sand grinders until the average particle size was
about 1.0 .mu.m.
Color Development Agent Dispersion (Solution A)
TABLE-US-00002 [0108] 4-Hydroxy-4'-isopropoxy diphenyl sulfone 6.0
parts (Nippon Soda Co., Ltd., D8) Aqueous solution of completely
saponified 18.8 parts polyvinyl alcohol (Kuraray Co., Ltd. PVA117,
solid content: 10%) Water 11.2 parts
Leuco Dye Dispersion (Solution B)
TABLE-US-00003 [0109] 3-Dibutylamino-6-methyl-7-anilinofluorane 2.0
parts (Yamamoto Chemicals Inc. ODB-2) Aqueous solution of
completely saponified 4.6 parts polyvinyl alcohol (Kuraray Co.,
Ltd. PVA117, solid content: 10%) Water 2.6 parts
Sensitizer Dispersion (Solution C)
TABLE-US-00004 [0110] 4-biphenyl-p-tolyl ether 4.0 parts (Nicca
Chemical Co., Ltd.) Aqueous solution of completely saponified 5.0
parts polyvinyl alcohol (Kuraray Co., Ltd. PVA117) Water 3.0
parts
[0111] Then, these dispersions were blended in the proportion
described below to prepare the thermosensitive recording layer
coating solution.
Thermosensitive Recording Layer Coating Solution
TABLE-US-00005 [0112] Color development agent dispersion (Solution
A) 36.0 parts Leuco dye dispersion (Solution B) 9.2 parts
Sensitizer dispersion (Solution C) 12.0 parts
[0113] This thermosensitive recording layer coating solution was
applied on one surface of the water-dispersible sheet prepared in
Example 1 with a coating weight (in solid) of 6.0 g/m.sup.2 and was
dried (at 50 degree C.) to form a thermosensitive recording layer,
then the sheet was subjected to a smoothing treatment so that its
Bekk smoothness was 500 to 1000 seconds to obtain a
water-dispersible sheet.
Example 121
[0114] The thermosensitive recording layer coating solution
prepared in the same manner as in Example 11 was applied on one
surface of the water-dispersible sheet prepared in Example 1. Then
the tacky adhesive layer of the release sheet prepared in the same
manner as in Example 10 was adhered to the other surface of this
water-dispersible sheet to prepare a water-dispersible sheet.
Comparative Example 11
[0115] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of removing CMC-Na salt from the
aqueous solution being applied on the hand-made paper by a size
press method.
Comparative Example 21
[0116] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of removing sodium carbonate (i.e.
alkalizing agent) from the aqueous solution being applied on the
hand-made paper by a size press method.
Comparative Example 31
[0117] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of preparing the hand-made paper
without using the fibrous CMC.
Comparative Example 41
[0118] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of using a carboxymethyl cellulose
sodium salt powder (trade name: Sunrose, manufactured by Nippon
Paper Industries Co., Ltd., Degree of etherification (DS) of 0.25,
viscosity of 75 mPa-s as 1% by weight aqueous solution at 20 degree
C.) as the CMC-Na salt.
Comparative Example 5
[0119] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of using a carboxymethyl cellulose
sodium salt powder (trade name: Sunrose, manufactured by Nippon
Paper Industries Co., Ltd., Degree of etherification (DS) of 0.7,
viscosity of 550 mPa-s as 1% by weight aqueous solution at 20
degree C.) as the CMC-Na salt.
Comparative Example 6
[0120] A water-dispersible sheet was prepared in the same manner as
in Example 1 with the exception of the amount of the CMC-Na salt
with respect to the hand-made paper being 18.0 wt %.
Comparative Example 7
[0121] A water-dispersible sheet was prepared in the same manner as
in Example 12 with the exception of removing CMC-Na salt from the
aqueous solution being applied on the hand-made paper by a size
press method.
[0122] The following evaluations were conducted on thus prepared
water-dispersible sheets. When evaluating the water dispersibility,
the release paper was removed before the evaluation.
1) Water Dispersibility
[0123] Five test pieces of 3 cm square were prepared from the
sample which had been conditioned in an atmosphere of 23 degree C.
and 50% RH for 24 hours or more. Then, one piece of the above test
piece was put into a 300 ml beaker with 300 ml of deionized water
while stirring at 650 rpm with a stirrer. The time when the test
piece was completely loosened into individual fibers and became
fibrous was measured with a stopwatch. Then the average value of
five measurements was taken as the water dispersion time. The
shorter the water dispersion time, the better the water
dispersibility.
2) Tensile Test
[0124] The tensile strength was measured according to Japanese
Industrial Standards (JIS) P8113 on the water-dispersible sheet
samples which had been conditioned in an atmosphere of 23 degree C.
and 50% RH for 24 hours or more.
3) Air Permeability
[0125] The volume of air passing through 1 cm.sup.2 surface of the
sample per minute with 100 mm H.sub.2O of the differential pressure
was measured by using the air permeability manual measuring
instrument (model PPM100 type, manufactured by Filtroner).
[0126] Table 1 shows the structure and the evaluation results of
the prepared water-dispersible sheets.
TABLE-US-00006 TABLE 1 Pulp sheet Coating Papermaking Fibrous
Alkalizing agent CMC-Na salt pulp CMC Amount against 1% Visicisity
Amount per Freeness Amount Amount pulp sheet at 20 degree pulp
sheet (mlCSF) (%) DS (%) (solid %) DS C. (mPa s) (solid %) Example
1 550 80 0.43 20 8.0 0.7 3 3.1 Example 2 650 80 0.43 20 8.0 0.7 3
3.1 Example 3 450 80 0.43 20 8.0 0.7 3 3.1 Example 4 550 80 0.43 20
8.0 0.9 28 3.1 Example 5 550 80 0.43 20 8.0 0.7 170 3.1 Example 6
550 80 0.43 20 9.3 0.7 3 1.9 Example 7 550 50 0.43 50 8.0 0.7 3 3.1
Example 8 250 30 0.43 70 10.5 0.7 3 4.2 Example 9 650 95 0.43 5 8.0
0.7 3 3.1 Example 10 550 80 0.43 20 8.0 0.7 3 3.1 Example 11 550 80
0.43 20 8.0 0.7 3 3.1 Example 12 550 80 0.43 20 8.0 0.7 3 3.1
Comparative 550 80 0.43 20 8.0 -- -- 0.0 Example 1 Comparative 550
80 0.43 20 0 0.7 3 3.1 Example 2 Comparative 550 100 -- 0 8.0 0.7 3
3.1 Example 3 Comparative 550 80 0.43 20 8.0 0.25 75 3.1 Example 4
Comparative 550 80 0.43 20 8.0 0.7 550 3.1 Example 5 Comparative
550 80 0.43 20 8.0 0.7 3 18.0 Example 6 Comparative 550 80 0.43 20
8.0 -- -- 0.0 Example 7 Evaluation result Tacky Thermosensitive
Water Tensile Air adhesive recording dispersion strength
permeability layer layer time (sec) (kN/m) (CORESTA) Example 1 --
-- 35 3.4 642 Example 2 -- -- 19 2.8 -- Example 3 -- -- 49 3.7 --
Example 4 -- -- 42 3.8 -- Example 5 -- -- 52 4.4 -- Example 6 -- --
41 3.3 -- Example 7 -- -- 17 3.5 -- Example 8 -- -- 51 2.5 --
Example 9 -- -- 34 3.0 -- Example 10 installed -- 36 3.3 -- Example
11 -- installed 108 6.6 -- Example 12 installed installed 114 6.5
-- Comparative -- -- 60 2.4 -- Example 1 Comparative -- -- longer
3.1 -- Example 2 than 300 Comparative -- -- longer 3.7 -- Example 3
than 300 Comparative -- -- 64 3.5 -- Example 4 Comparative -- --
longer 4.3 139 Example 5 than 300 Comparative -- -- 75 5.9 --
Example 6 Comparative installed installed 195 4.7 -- Example 7
[0127] It is derived from Table 1 that a water-dispersible sheet
with further improved water dispersibility can be obtained by using
two kinds of compounds, a specific alkalized fibrous carboxyalkyl
cellulose and a specific carboxyalkyl cellulose sodium salt.
[0128] On the other hand, when using a carboxymethyl cellulose
sodium salt with high-viscosity, the air permeability is suppressed
and the water dispersibility is also deteriorated, thus the object
of the present invention can not be achieved (see Comparative
Example 5).
* * * * *